As top marine predators, marine mammals (seals, dolphins, whales) accumulate staggering levels of pollutants in their tissues and are important indicators or “sentinel species” for contamination of the ocean food web. High levels of endocrine-disrupting chemicals have been linked with hormonal abnormalities, skeletal deformities, reproductive failure, and population declines, while immunotoxic chemicals such as PCBs and flame retardants are widely suspected to contribute to the recurring disease outbreaks that have decimated several populations.
Since 2000, the Marine & Environmental Research Institute has conducted Seals As Sentinels, a long-term research project examining levels, effects, and trends of toxic contaminants in marine mammals and fish in the northwest Atlantic. This landmark project has generated the first extensive, region-wide body of contaminants data in harbor seals and commercially important marine fish stocks from Maine to New York and has earned national and international recognition.
Today, our ongoing research is driven by the concern that toxic chemical stress may be contributing to the recurring disease outbreaks and mortalities affecting the population.
Surprising Study of PCBs in Harbor Seal Pups
Of the hundreds of chemicals we have analyzed since 2001, the industrial chemicals polychlorinated biphenyls (PCBs) were by far the major contaminants in harbor seals. Banned over 40 years ago, PCBs are extremely persistent in the ocean and releases are still permitted from sources like old transportation equipment, transformers, and landfills.
PCBs are potent immune system suppressants that were linked to the die-offs of tens of thousands of European seals.
An earlier study (Shaw et al. 2005) showed that PCB levels in harbor seals declined since the extremely high levels of the 1970s, but levels have remained steady since the mid-1980s. In 2011, we launched a follow-up study which yielded many unexpected results.
With tissues from our Environmental Specimen Bank, we analyzed PCBs in 50 harbor seal pups that had stranded between 2001 and 2006 along the Atlantic coast from Maine to Massachusetts. To our surprise, PCB levels in seal pup tissues are higher than ever, especially in the liver.
PCB levels in our harbor seal pups are more than 1,000 times higher than levels known to suppress normal immune responses in young harbor seals.
Clearly, PCBs still pose a major health threat to our harbor seal pups during vulnerable stages of life, which raises concern for the future of the population. Through our Seals As Sentinels studies, we will continue tracking body burdens of PCBs, flame retardants, and other toxic contaminants in our harbor seals to monitor the effects of toxic stress on their health.
Flame Retardants and Their Chemical Cousins
In 2004, we began to study flame retardant chemicals in farm-raised and wild salmon. In 2007, our scientists were the first to discover that brominated flame retardant chemicals from household furniture (PBDEs) had contaminated marine top predators (harbor seals and seven species of commercial fish) in the northwest Atlantic Ocean.
Levels of PBDE flame retardants were so high in tissues that we reported our harbor seals are effectively "fire-retarded"
In 2010, we published a major review that found these halogenated flame retardants are not only hazardous to animal and human health, but they are ineffective in preventing fire deaths (Shaw et al. 2010). This paper resulted in the San Antonio Statement calling for global regulation of the chemicals, signed by 300 scientists from 30 countries (DiGangi et al. 2010).
Because of their toxicity and persistence, many PBDEs were phased-out of use, but new and untested flame retardants were quickly introduced as replacements. But the replacements are “chemical cousins” to PBDEs and therefore likely to be just as harmful.
Our latest study measures “replacement” flame retardants in 40 harbor seal pups that stranded along the Atlantic coast from Maine to Massachusetts between 2001 and 2010. From our data, it appears that these “new” untested flame retardants, like the PBDEs, have migrated from households into the ocean and are accumulating in marine top predators.
In 2007, the Institute received a Citation of Recognition from the the 123rd Maine State Legislature for Seals As Sentinels research. Our finding of brominated flame retardants (BFRs), including the neurotoxic deca-BDE, in harbor seals and fish supported the Maine legislature’s decision to ban Deca from children’s products as of 2010.
The program also received recognition from the Gulf of Maine Council on the Marine Environment representing New England states and Atlantic Canada. Named Gulf of Maine Visionary, the Institute’s Director, Dr. Susan Shaw was recognized for "creating a world-class research institute uniquely dedicated to environmental issues affecting the Gulf of Maine and for generating an extensive body of data that places the Gulf ecosystem in a global perspective."
To learn more about our Seals As Sentinels research, click below:
- Brominated Flame Retardants in the NW Atlantic Marine Food Web
- Perfluorinated Compounds (PFCs) in NW Atlantic Harbor Seals
- Brominated Flame Retardants (PBDEs) in NW Atlantic Harbor Seals [ 1 | 2 ]
- PCBs and Chlorinated Pesticides in NW Atlantic Harbor Seals
- Assessing Dioxin-like Compounds in Harbor Seals
- Dioxin-like Compounds and Immune Responses in Free-Ranging Harbor Seals
- Heavy Metals and Trace Elements in Northwest Atlantic Harbor Seals
- Seasonal Patterns of Prey Fish Consumption by Gulf of Maine Harbor Seals
- Shaw and Kannan 2009 Review paper